(Applicant's Abstract) The overall objective of the Clinical Core is to provide the personnel, physical resources and organization required to generate the clinical database and biologic specimens for projects I through 5. The Clinical Core will be responsible 1) for the design, implementation and execution of clinical research protocols within the SCOR, 2) for interactions between investigators in the various projects and 3) for data collection, data management and statistical analysis. A proposed clinical protocol incorporates state-of-the-art methods for diagnosis and treatment of idiopathic pulmonary fibrosis JPF) and assessment of its response to therapy. The specific aims are as follows: To execute clinical protocols involving patients with idiopathic pulmonary fibrosis. Recruit eligible patients with IPF from UCLA and its network affiliates in the Los Angeles area Acquire and review pre-screening data for initial assessment of study eligibility. Obtain informed consent, collect clinical data and perform pulmonary function testing Obtain and score chest radiographs and thoracic high resolution computerized tomographs Determine eligibility for enrollment into run-in phase (prednisone therapy for 3 months) Repeat clinical, radiographic and physiologic assessments at specified intervals Determine eligibility for randomization and randomize eligible patients into the treatment phase Manage randomized patients on study treatment regimens (interferon -gamma [IFN-gamma] plus low-dose prednisone vs. azathioprine [AZAI plus low-dose prednisone), monitor toxicity and formally assess response to therapy at 3- month intervals using CRP assessment tools To procure lung tissue and bronchoalveolar lavage fluid and cells. Handle and transport lung biopsy specimens from IPF patients to the Tissue Pathology Core Perform fiberoptic bronchoscopy at randomization and at 6 and 12 months after initiation of study treatment and at the time of relapse in patients whose disease worsens after discontinuation of IFN-gamma or AZA. Handle and transfer bronchoalveolar lavage fluid and cells and transbronchial biopsy specimens to the Tissue Pathology Core.